1. Field of the Invention
The present invention relates to a projection display system and a projector, and more particularly to a projection display system and a projector which can be used in various occasions including conferences, presentations, training courses, educational events, etc., can effectively utilize space, and can easily be installed in place.
2. Description of the Related Art
It is the general practice today for attendants at conferences, presentations, training courses, etc., to project images, characters, information, etc., onto a large screen and give oral explanations using some display devices. There are available various display devices, and a suitable one is chosen depending on the size of the place where it is used and the number of people who attend the occasion.
Generally, front-projection projectors are often used in wide places attended by many people. Smaller places attended by fewer people see more opportunities to use rear-projection projectors, plasma display units, CRT display units, liquid crystal units, and TV sets.
There have been growing demands for display devices for displaying information such as images or the like on a large screen in meetings and training sessions that take place in small rooms and attended by a few people.
FIGS. 1A and 1B of the accompanying drawings illustrate a conventional projection display system which uses a front-projection projector in a small room. FIG. 1A is a plan view of the conventional projection display system as viewed from the ceiling, and FIG. 1B is a side elevational view of the conventional projection display system.
FIGS. 1A and 1B show a meeting room where a single table is placed and surrounded by a space large enough for 34 meeting attendants (observers) to be seated. Actually, there are many meeting rooms having such a meeting space. In recent years, particularly, offices or the like have many small rooms that are divided by partitions.
As shown in FIGS. 1A and 1B, general front-projection projector 32 is placed on upper surface panel 33 of a table that is put on floor 36 of such a small meeting room. Documents are spread or work is done on upper surface panel 33 of the table.
Light emitted from projector 32 as indicated by light path 7 is projected onto a partition wall of the room or screen 35 installed thereon.
Display devices other than the front-projection projector for use in such small meeting rooms include liquid crystal display devices that can be carried around. The liquid crystal display devices are generally small in screen size and tend to make the viewer uncomfortable watching projected images. It is preferable for liquid crystal display devices to have a screen size of 35 inches or more.
Recently, there are liquid crystal display devices having a large screen size. However, liquid crystal display devices with a larger screen size are heavier and make themselves hard to be carried around, as with plasma display devices and CRT display devices. Fixed installation of a large-screen display device that cannot be carried around in a small room as shown in FIGS. 1A and 1B is economically wasteful and not practical. Therefore, a front-projection projector that can easily be carried around is used in such a small room.
The front-projection projector is a projector for displaying image light that has passed through an optical system on a front screen at an enlarged scale. Technical details of the front-projection projector are disclosed in Japanese laid-open patent publication No. 6-237429, for example.
With the front-projection projector used in the conventional fashion as shown in FIGS. 1A and 1B, the projector is placed on the meeting table and the light path from the projector passes over the meeting table. Therefore, if an object is placed on the table or notes are taken on the table, then shadows are produced on the projected image on the screen. The space occupied by the projector itself and the space taken up by the projected light pose a limitation on the space available on the table, which cannot freely be used by the attendants.
Environments for using projectors in spaces smaller than the space shown in FIGS. 1A and 1B are problematic in that a sufficient space may not be available for the installation of a projector or enough space may not be available for the light path from a projector.